Among the different ways permitting the boosting the culinary item's resistance to detergents used in the dishwasher the one shown by document US 2003/0138661 can be mentioned.
This state of the art describes specifically a culinary item presenting improved hydrophobic properties, said culinary item including a support element and a first coating, said first coating being deposited on at least one first face of the support element and being obtained by the application, then the baking, of at least one coat of a sol-gel composition.
The use of a sol-gel composition provides some hydrophobic properties to the first coating and therefore at least to the support element face of the culinary item provided with this first coating. In fact, as indicated in the document US 2003/0138661, the sol-gel composition permits implementing a protective coat that adheres to the support element, which is transparent and confers a durable chemical resistance to the support element thus covered.
A sol-gel composition is understood as a composition including a suspension or a colloidal solution of solid particle or precursors in a solvent, which by aggregation of particles, leads to the formation of a gel then to a solid, this aggregation being classically obtained under the action of a catalyst and/or temperature.
Sol-gel compositions described in the document US 2003/0138661 implement a colloid suspension of solid particles in an organic solvent, such as an alcohol. The solid particles considered by this document are the hydrolysed metallic alkoxides, in particular of titanium, zirconium, aluminium and/or silicon.
In this state of the art the sol-gel compositions are indiscriminately applied on metallic support elements, specifically on aluminium, cast-iron, steel and stainless steel. Such support elements are indicated as being either smooth, brushed or anodised in the particular case of aluminium.
However, experience shows that any type of sol-gel composition, that meets the definition given above by the document US 2003/0138661, does not allow satisfactory hydrophobic properties to be obtained.
This fact is even more true since the detergents used today in dishwashers have more and more aggressive formulations in order to optimise the cleaning performance. Such formulations combine in effect an ever higher alkalinity with the generation of nascent oxygen.
The problem posed by this invention is therefore to remedy the above mentioned drawbacks, by proposing a culinary item compatible with a cleaning method in dishwashers, even in the presence of a particularly aggressive detergent.
One solution to this problem posed is therefore to propose a culinary item presenting improved hydrophobic properties, specifically an improved resistance to detergents used in dishwashers, said culinary item include a support element and a first coating, said first coating being deposited on at least one first face of the support element and being obtained by the application, then the baking, of at least one coat of a sol-gel composition, characterised in that it also includes at least one second coating deposited on the first coating, said second coating being obtained by the application, then the baking, of at least one coat of a silicone-based compound.
In a surprising fashion, the applicant found that the realization, on a first coating obtained from a sol-gel composition, of a coating obtained from a silicone-based composition allowed the hydrophobic properties already conferred by the first coating to be considerably improved.
The method of depositing, on a first sol-gel based coating previously deposited on a metallic substrate a second coating intended to fill the pores of the first coating is known to those skilled in the art.
Thus, DE 10163646 describes an inorganic material for surface coating containing:
a substrate, that can be metallic, partially or completely covered;
a porous coating, for example a sol-gel material presenting hydrophobic properties; and
a second coating, realized in a nanocomposite material, that is deposited on the porous coating to fill its pores, this second coating presenting a better mechanical behaviour than the porous coating.
However, DE 10163646 recommends not to use a silicone-based material, because it is softer and less stable from a mechanical viewpoint than a material of a nanocomposite type.
However, the applicant discovered in a surprising and unexpected manner, that if a coat obtained from a silicone is deposited over a first coating of sol-gel type, the first coating behaves as a primary base coat for this second coating that adheres thereto perfectly, and the mechanical adherence of the assembly is improved.
The culinary item according to the invention must also preserve over time, at least for the first face of the coated support element of the first coating, a similar appearance to that of a culinary item without such a first coating and not to deteriorate following repeated cleaning cycles in a dishwasher.